Guitar String Tension Calculator
Calculate guitar string tension in lbs and kg from scale length, tuning frequency in Hz, and gauge.
Shows the effect of tuning down or changing string gauge.
String Tension
String tension determines how hard a string pulls on the guitar or instrument neck, affecting playability, tone, and neck relief. Knowing the tension helps you choose string gauges that balance feel and sound.
The Formula:
T = (UW × 2 × L × F)² / 386.4
Where:
- T = tension in pounds
- UW = unit weight of string (pounds per inch, from manufacturer data)
- L = scale length in inches
- F = frequency (Hz) of the open string
- 386.4 = constant (converts units correctly)
Standard Tuning Frequencies (Hz):
| String | Note | Frequency |
|---|---|---|
| 1 (high E) | E4 | 329.63 Hz |
| 2 (B) | B3 | 246.94 Hz |
| 3 (G) | G3 | 196.00 Hz |
| 4 (D) | D3 | 146.83 Hz |
| 5 (A) | A2 | 110.00 Hz |
| 6 (low E) | E2 | 82.41 Hz |
Worked Example:
Electric guitar, 25.5" Fender scale length. High E string, 0.009" gauge.
UW for 0.009" plain steel ≈ 0.0000635 lb/in
T = (0.0000635 × 2 × 25.5 × 329.63)² / 386.4 T = (1.0703)² / 386.4 T = 1.1455 / 386.4 = 16.1 lbs
Typical Total String Set Tensions:
| String Gauge | Guitar Type | Total Tension (all 6 strings) |
|---|---|---|
| 8–38 | Electric | ~50–60 lbs |
| 9–42 | Electric | ~60–75 lbs |
| 10–46 | Electric | ~75–90 lbs |
| 12–53 | Acoustic | ~130–165 lbs |
Practical Tips:
- Higher tension = brighter tone, more volume, higher action required
- Lower tension = easier bending, faster play, more prone to buzzing
- Changing to a significantly different gauge may require neck relief adjustment and intonation reset
- Baritone and extended range guitars need heavier strings tuned lower to maintain appropriate tension